Thermodynamics and Metabolism

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Thermodynamics and Metabolism
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Thermodynamics the science of energy
transformations (flow of energy through living
and non-living systems)
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All living things require ENERGY which is the
capacity for doing work

• Forms of energy
• thermal
• light
• chemical
• electrical

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KINETIC ENERGY

• Energy of motion
• Falling water
• Pistons in a car engine
• Skier going down a hill
• Examples on a molecular scale include the energy
  of vibrations, random diffusion, and heat.

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POTENTIAL ENERGY

• stored energy
• Example Molecules of glucose have potential
  energy, stored in bonds

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FIRST LAW OF THERMODYNAMICS

• Energy can neither be created nor destroyed, but
  can be transformed from one form to another.
• eg during photosynthesis, light energy from the
  Sun is transformed into chemical energy stored in
  the bonds of glucose

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• During cellular respiration, the energy in the
  bonds of glucose is released and is transformed
  into new molecules (ATP), motion, and heat energy.

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Photosynthesis and Respiration Photosynthesis and Respiration
     Photosynthesis      Respiration
produces food stores energy uses water uses carbon dioxide releases oxygen occurs in sunlight uses food releases energy produces water produces carbon dioxide uses oxygen occurs in the dark as well as light
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The Second LAW OF THERMODYNAMICS Every energy
transformation increases the entropy of the
universe.

• There is ALWAYS some loss of useful energy.

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The second law of thermodynamicsIn all
processes or reactions, some of the energy
involved irreversibly loses its ability to do
work. orIn any reaction the amount of
molecular disorder always increases
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Entropy is a measure of the randomness or
disorder in a collection of objects

• Entropy increases
• when solids become liquids or gases
• Complex molecules react to form simpler molecules
  (catabolic reactions)
• During diffusion

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Living systems seem to break the second Law of
Thermodynamics

• Anabolic processes in cells build highly ordered
  structures (e.g. proteins and DNA) from a random
  assortment of molecules (amino acids and
  nucleotides) in the cell fluids.

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• On a large scale, living organisms build and
  maintain highly ordered structures such as cells,
  tissues, organs and systems, as well as nests,
  webs and homes.
• All of these changes cause the universe to become
  a little more ordered.

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But these anabolic processes are coupled to
catabolic processes

• Which release free energy and thermal energy and
  increase the entropy of the universe.
• Living organisms create order in a local part of
  the universe at the expense of greater a greater
  amount of disorder in the universe as a whole.

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Free energy       It is clear that we should be
concerned only with energy available to do useful
work, so-called free energy or Gibbs energy.
Josiah WillardGibbs(1839 - 1903)
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• Exothermic Reactions
• Produce energy (exergonic reactions)
• Tend to increase entropy (therefore, spontaneous)
• - delta G value
• E.g. cellular respiration

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Exothermic Reaction
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• B) Endothermic Reactions
• Require energy (endergonic reactions)
• Tend to decrease entropy (because they create
  big/organized molecules)
• Are not spontaneous
• delta G values
• E.g. photosynthesis

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The Transition state describes the temporary
conditions in which the bonds within reactants
are breaking and the bonds between products are
forming.
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Activation Energy (EA) amount of energy needed
to strain and break the reactants' bonds in a
biochemical reaction
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For an exergonic reaction, DG is negative.For an
endergonic reaction, DG is positive.
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ATP

• ATP is the primary source of free energy in
  living cells.

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• ATP transports chemical energy within cells for
  metabolism.
• Metabolic processes that use ATP as an energy
  source convert it back into ADP and inorganic
  phosphate(Pi) precursors.
• ATP is therefore continuously recycled in
  organisms the human body, contains 250 grams of
  ATP on average, and turns over its own weight in
  ATP each day.

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Phosphorylation

• When ATP is used as an energy source, the energy
  is NOT released as heat.
• Instead, the hydrolysis of ATP is usually coupled
  to a reaction which attaches the phosphate group
  to another molecule directly associated with the
  work that needs to be done. (What example of this
  have you seen?)
• Attaching the phosphate group (phosphorylation)
  makes the other molecule more reactive

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Redox reactions

• In living systems, free energy must be released
  in small quantities.
• The hydrolysis of ATP and the phosphorylation of
  molecules is one way to accomplish this,
• Another is coupled oxidation-reduction reactions.
  

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• The transfer of electrons ( and H) from one
  substance to another is a way of transferring
  free energy.
• The electronegativity of each substance in the
  chain must be greater than the molecule that
  preceded it.
• Redox reactions are used to create ATP.